1. Field of the Invention
The present invention relates to an x-ray tube with a cathode and an anode arranged in a vacuum housing wherein the electron beam emanating from the cathode is incident at a focal spot on the anode, of the type wherein means for deflecting the electron beam are provided.
2. Description of the Prior Art
The possibility of deflection of the electron beam and thus deflecting the focal spot is of particular importance in connection with computed tomography since, as is known, by displacing the focal spot between two end (extreme) positions an improvement in the image quality can be achieved due to the thusly achieved multiplication of the data available for the calculation of the image of a body slice.
An x-ray tube of the abovementioned type is described in German OS 41 25 926, wherein the means for deflection of the electron beam are formed by an air coil arranged outside the vacuum housing. This air coil is designed in a manner which causes it to occupy a considerable volume. In addition, considerable electrical power must be fed to the air coil to effect a defined deflection of the electron beam, so that a great deal of dissipated heat is released in undesirable fashion in connection with the deflection of the electron beam, which presents a further disadvantage in view of the thermal problems arising in the operation of x-ray tubes anyway. Nevertheless, the air coil has good transmitting properties even in the case of actuation with signals of higher frequency or with signals containing portions of higher frequency. Such signals are employed in new computed tomography systems for deflection of the electron beam.